Expandable form for hollow-core concrete construction



3 Sheets-Sheet 1 H. D. BURDETT r Y m E N M E P 0 0. T .2 m A p. 0 ...|..P MN m w 3 4 m 2 l I 7 x Md .w fl w x w IIIIIIIII H s-E Nov. 4, 1969 EXPANDABLE FORM FOR HOLLOW-CORE CONCRETE CONSTRUCTION Filed July 5, 1967 Nov. 4, 1969 H. D. BURDETT 3, 76,

EXFANDABLE FORM FOR HOLLOW-CORE CONCRETE CONSTRUCTION 3 Sheets-Sheet 2 July 5, 196'? R H a. a s m a N 4 a 7. 6 2 75 .1 0 3 1 3 7 3 1 a, 8 M a ,J 2 a (J6 1 1O \I. 13 4.; E 5 2 f M 0 w N 5 e 4 8 o 7 3 W 3 5 k a 9 f i Z 2 J I. a I I ll 4 a l (I I 2/ 3 2 9 3 4 2 7 Q 3 2 a 4. n a 4 H 1 g q. Q 4 7 a a w 5 4 5 8 3 a u 5 n a 4 1 K w 3 7 2 3 2 v 3 2 4 x A a f 1 8 y a A 4 Nov. 4, 1969 H. D. BURDETT 3,476,351

EXPANDABLE FORM FOR HOLLOW-CORE CONCRETE CONSTRUCTION Filed July Z, 1967 3 Sheets-Sheet 5 51 7 j-I 1 A.

INVENTOR. 51 14442040 0. 5020577 ATTORNEY United States Patent O 3,476,351 EXPANDABLE FORM FOR HOLLOW CORE CONCRETE CONSTRUCTION Harold D. Burdett, 3802 S. Grandview Drive, Tempe, Ariz. 85281 Filed July 3, 1967, Ser. No. 650,758 Int. Cl. B28b 7/30 US. Cl. 249-82 6 Claims ABSTRACT OF THE DISCLOSURE An expandable and collapsible concrete form for forming the inner core of hollow-core concrete structures which automatically compensate for the normal shrink age of the concrete during the curing process by inward deflection of the form to thereby prevent cracks occurring in the completed concrete structure. After the curing process is complete, the compensating expandable form may be collapsed for ease of removal BACKGROUND OF THE INVENTION (1) The field of this invention lies in the construction of hollow-core concrete structures, and is particularly directed to a reuseable inner form device which automatically compensates for shrinkage of the curing concrete.

(2) Heretofore it has been necessary to hand-erect and dis-assemble the forms required to construct hollowcore concrete structures by very costly and time consuming operations.

Furthermore, these forms are of rigid construction and make no allowance or automatic compensation for the normal shrinkage of concrete during the curing process.

Other prior art devices for hollow-core concrete con struction have been complex mechanically driven machines which are not portable, require transporting the completed concrete structure to the building site, and have a highly undesirable characteristic due to the great weight.

SUMMARY OF THE INVENTION In applicants invention it is an object to provide a hollow-core form for concrete construction which is portable and requires a minimum amount of set-up time.

Another object of this invention is to provide a hollowcore form for concrete construction which is collapsible for ease of removal.

Still another object of this invention is to provide a hollow-core form for concrete construction which will automatically compensate for the shrinkage of the curing concrete.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary perspective view showing a collapsible form for hollow-core concrete construction incorporating the features of this invention.

FIG. 2 is a fragmentary perspective view of a high rise concrete building illustrating some of the areas in which the present invention may be utilized.

FIG. 3 is a side elevation, partially broken away, to show the inner structure of the hollow-core form of FIG. 1.

FIG. 4 is an enlarged sectional view on the line 4-4 of FIG. 3.

FIG. 5 is an enlarged sectional view similar to FIG. 4 but showing the hollow-core form collapsed.

FIG. 6 is an enlarged fragmentary sectional view particularly illustrating the automatic compensating deflection characteristics of the hollow-core form.

Patented Nov. '4, 1969 DESCRIPTION OF THE PREFERRED EMBODIMENT As an example of a preferred embodiment of the invention there is shown a hollow-core form indicated generally at 10 having four diametrically opposed corner members 11, 12, 13 and 14 with concrete engaging portions 15 and 16 and inwardly depending cam portions 17 and 18. Frictionally interconnecting adjacent corner members 11, 12, 13 and 14 are side form members 19, 20, 21 and 22 having concrete engaging surfaces 23, and cam surfaces 24-25 slidably engaging cam portions 17-18 of corner members 11, 12, 13 and 14.

Axially arranged within the hollow-core form 10 is a square tubular frame member 26 which interconnects axially spaced form actuator mechanisms indicated generally at 27. Member 26 contains a main shaft 28 on which is axially slidably mounted actuating cylinder 29. Axial movement of cylinder 29 from broken line position 30 to solid line position 31, of FIG. 3, will simultaneously expand the actuator mechanism 27 as will hereinafter be described in detail.

Fixed to peripheral surface 32 of cylinder 29 are clevises 33 to which are pivotally connected actuator arms 34 which extend outwardly through guide slots 35 in frame 26, and are pivotally connected at their opposite ends to inwardly depending clevises 36, suitably attached at the intersection of inner surfaces 37-38 of concrete engaging portions 15-16 of corner members 11-12-13 and 14.

In order that hollow-core form 10 may be actuated to the expanded state as shown best in FIGS. 3-4, it is necessary that an actuation force (not shown) be applied in the direction of arrow 39, FIG. 3, to cause arms 34 to move, in the direction of the applied force, through the guide slots 35 of member 26 until they engage stop portions 40 of guide slots 35. At this point the arms 34 will have moved to dead center with comer members 11-12-13-14 in their extended position, FIG. 4. The wedge action of corners 11-12-13-14 during their movement will carry side members 19-20-21-22 to the expanded position where they are held by the biasing action of tension springs 41, one end being suitably attached to the inner surfaces 42 of side form members 19-20-21-22, the other end of which is suitably attached to member 26 at points 43.

Stability of side forms 19-20-21-22 is accomplished by inward-1y depending guide sleeves 44 suitably attached to surfaces 42 and having peripheral surfaces 45 slidably engaging the bores 46 of guide sleeves 47 suitably attached to member 26.

To operate the preferred embodiment of the present invention the hollow-core form 10 is placed in the desired position and held there by main shaft 28. Hollowcore form may then be actuated to its extended position as hereinbefore described. The remaining external forms 48 may then be erected as required by the particular job to be undertaken. The concrete 49 is then poured into position as shown best in FIG. 4. Upon completion of the curing process the hollow-core form 10 is collapsed, as best seen in FIG. 5, by reversing the previously described actuating procedure, and may then be easily removed.

The action of hollow-core form 10 in automatically compensating for normal shrinkage of the curing concrete may best be seen in FIG. 6. The shrinking concrete exerts a force in the direction of arrows 50, which is exerted against the outside surfaces 23 of side forms 19-20- 21-22 deflecting them inwardly in the direction of arrow 50. The corners 11-12-13-14 at this time are being held rigidly in place by arms 34, but the force applied to cam portions 17-18 by cam surfaces 24-25 of side forms 19-2021-22 plus the shrinkage force against the surfaces-16 will cause the corners 11-12-1344 to deflect inwardly in the direction of the arrows 52 to the broken line position 51.

While the apparatus herein disclosed and described constitutes a preferred form of the invention, it is also to be understood that the apparatus is capable of mechanical alteration without departing from the spirit of the invention, and that such mechanical arrangement and commercial adaptation as fall within the scope of the appended claims are intended to be included herein.

- I claim: 1

1. An expandable form for hollow-core casting which comprises in combination:

(a) frame member,

. (b) a plurality of inside corner forming members radially movable on said frame member,

(c) a plurality of side members angularly engaging said corner forming members,

(d) yielding means for interconnection between said frame member and each of said side members for normally urging said side members into engagement with said corner forming members,

(e) and an actuation means on said frame member connected to said corner member so as to expand and collapse said corner forming members while moving said side members radially to and from collapsed position.

2. An expandable form as in claim 1 wherein said actuation means includes:

(a) a main shaft axially located and fixed relative to said frame member,

(b) an actuating cylinder slidably mounted on said main shaft,

(c) and a plurality of actuator arms pivotally attached at one end to said actuating cylinder and movably supported on said frame member and having the other end pivotally attached to said corner members so that axial movement of said actuation cylinder will expand and collapse the hollow-core form.

3. An expandable form as in claim 1 wherein said yielding means is a tension means for holding said plurality of side members in said angular engagement with said corner members.

4. An expandable form as in claim 1 including:

(a) an angularly disposed cam surface means on said corner members,

(15) a mating cam surface means on said side members slidingly engaging said cam surface means of said corner members so that cast material shrinkage forces will inwardly move said side members and so that said cam surfaces of said side members will deflect said cam surfaces of said corner members.

5. An expandable form as set forth in claim 1 wherein (a) a said frame member being tubular and axially arranged within said expandable hollow-core form, and wherein said actuation means comprises:

(b) a main shaft axially positioned within said frame member,

(c) a cylindrical actuating member slidably axially on said main shaft,

(d) and a plurality of radially disposed actuator arms pivotally attached at one end to said actuating member and extending through said frame member and having the other end pivotally attached to said plurality of corner members so that axial reciprocation of said actuation member will expand and collapse said hollow-core form.

6. An expandable form as in claim 1 wherein said means for urging said plurality of side members in engagement with said corner forming members comprises a tension spring attached to each said side members and to said frame member including guide means on said frame member to support said side member for radial movement relative to said frame member.

References Cited UNITED STATES PATENTS 1,060,188 4/1913 Jacobson. 1,312,157 8/1919 Buente 249181 1,390,104 9/ 1921 Emmrich 249-152 1,795,021 3/1931 Goin 249181 2,405,254 8/ 1946 Hopkins 249- 2,543,892 3 /1951 Carpenter 249-144 2,827,683 3/ 1958 Benart et al. 3,064,439 11/1962 Cobi, 3,279,740 10/ 1966 Long 249151 FOREIGN PATENTS 93,754 6/ 1962 Denmark.

624,161 3/ 1927 France.

1,243,315 8/1960 France.

84,441 6/1921 Germany.

412,467 5/ 1925 Germany.

166,299 7/1921 Great Britain.

552,917 4/ 1943 Great Britain.

560,156 4/ 1957 Italy.

J. HOWARD FLINT, JR., Primary Examiner US. Cl. X.R. 249181 

